Jacob Shen, a graduate student at the California Institute of Technology, Josh Borrow, a postdoc at the Massachusetts Institute of Technology, and their co-authors asked, How do early-universe galaxies born inside alternative dark matter halos start out, and what happens as they grow?

In an April paper uploaded to the preprint server arXiv.org and submitted to the Monthly Notices of the Royal Astronomical Society, a group of theorists simulated how primordial galaxies would look if they formed inside clouds of three different types of alternative dark matter: “warm” dark matter, “fuzzy” dark matter and “interacting” dark matter with acoustic oscillations. By comparing them against cold dark matter galaxy simulations, the researchers discovered odd structural and chemical differences, galactic tweaks that the James Webb Space Telescope (JWST) might be able to see.

“On larger scales, everything is consistent with [cold dark matter],” says Romeel Dave, an astronomer at the University of Edinburgh in Scotland, who was not involved in the research. “But questions arise when you start to go to very small scales.”

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